Publications by authors named "Andrew M Holwerda"

34 Publications

The impact of collagen protein ingestion on musculoskeletal connective tissue remodeling: a narrative review.

Nutr Rev 2021 Oct 4. Epub 2021 Oct 4.

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, The Netherlands.

Collagen is the central structural component of extracellular connective tissue, which provides elastic qualities to tissues. For skeletal muscle, extracellular connective tissue transmits contractile force to the tendons and bones. Connective tissue proteins are in a constant state of remodeling and have been shown to express a high level of plasticity. Dietary-protein ingestion increases muscle protein synthesis rates. High-quality, rapidly digestible proteins are generally considered the preferred protein source to maximally stimulate myofibrillar (contractile) protein synthesis rates. In contrast, recent evidence demonstrates that protein ingestion does not increase muscle connective tissue protein synthesis. The absence of an increase in muscle connective tissue protein synthesis after protein ingestion may be explained by insufficient provision of glycine and/or proline. Dietary collagen contains large amounts of glycine and proline and, therefore, has been proposed to provide the precursors required to facilitate connective tissue protein synthesis. This literature review provides a comprehensive evaluation of the current knowledge on the proposed benefits of dietary collagen consumption to stimulate connective tissue remodeling to improve health and functional performance.
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http://dx.doi.org/10.1093/nutrit/nuab083DOI Listing
October 2021

Daily Myofibrillar Protein Synthesis Rates in Response to Low- and High-Frequency Resistance Exercise Training in Healthy, Young Men.

Int J Sport Nutr Exerc Metab 2021 Feb 17;31(3):209-216. Epub 2021 Feb 17.

University of Birmingham.

The impact of resistance exercise frequency on muscle protein synthesis rates remains unknown. The aim of this study was to compare daily myofibrillar protein synthesis rates over a 7-day period of low-frequency (LF) versus high-frequency (HF) resistance exercise training. Nine young men (21 ± 2 years) completed a 7-day period of habitual physical activity (BASAL). This was followed by a 7-day exercise period of volume-matched, LF (10 × 10 repetitions at 70% one-repetition maximum, once per week) or HF (2 × 10 repetitions at ∼70% one-repetition maximum, five times per week) resistance exercise training. The participants had one leg randomly allocated to LF and the other to HF. Skeletal muscle biopsies and daily saliva samples were collected to determine myofibrillar protein synthesis rates using 2H2O, with intracellular signaling determined using Western blotting. The myofibrillar protein synthesis rates did not differ between the LF (1.46 ± 0.26%/day) and HF (1.48 ± 0.33%/day) conditions over the 7-day exercise training period (p > .05). There were no significant differences between the LF and HF conditions over the first 2 days (1.45 ± 0.41%/day vs. 1.25 ± 0.46%/day) or last 5 days (1.47 ± 0.30%/day vs. 1.50 ± 0.41%/day) of the exercise training period (p > .05). Daily myofibrillar protein synthesis rates were not different from BASAL at any time point during LF or HF (p > .05). The phosphorylation status and total protein content of selected proteins implicated in skeletal muscle ribosomal biogenesis were not different between conditions (p > .05). Under the conditions of the present study, resistance exercise training frequency did not modulate daily myofibrillar protein synthesis rates in young men.
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http://dx.doi.org/10.1123/ijsnem.2020-0274DOI Listing
February 2021

Exercise Plus Presleep Protein Ingestion Increases Overnight Muscle Connective Tissue Protein Synthesis Rates in Healthy Older Men.

Int J Sport Nutr Exerc Metab 2021 Feb 14;31(3):217-226. Epub 2021 Feb 14.

Maastricht University Medical Centre.

Protein ingestion and exercise stimulate myofibrillar protein synthesis rates. When combined, exercise further increases the postprandial rise in myofibrillar protein synthesis rates. It remains unclear whether protein ingestion with or without exercise also stimulates muscle connective tissue protein synthesis rates. The authors assessed the impact of presleep protein ingestion on overnight muscle connective tissue protein synthesis rates at rest and during recovery from resistance-type exercise in older men. Thirty-six healthy, older men were randomly assigned to ingest 40 g intrinsically L-[1-13C]-phenylalanine and L-[1-13C]-leucine-labeled casein protein (PRO, n = 12) or a nonprotein placebo (PLA, n = 12) before going to sleep. A third group performed a single bout of resistance-type exercise in the evening before ingesting 40 g intrinsically-labeled casein protein prior to sleep (EX+PRO, n = 12). Continuous intravenous infusions of L-[ring-2H5]-phenylalanine and L-[1-13C]-leucine were applied with blood and muscle tissue samples collected throughout overnight sleep. Presleep protein ingestion did not increase muscle connective tissue protein synthesis rates (0.049 ± 0.013 vs. 0.060 ± 0.024%/hr in PLA and PRO, respectively; p = .73). Exercise plus protein ingestion resulted in greater overnight muscle connective tissue protein synthesis rates (0.095 ± 0.022%/hr) when compared with PLA and PRO (p < .01). Exercise increased the incorporation of dietary protein-derived amino acids into muscle connective tissue protein (0.036 ± 0.013 vs. 0.054 ± 0.009 mole percent excess in PRO vs. EX+PRO, respectively; p < .01). In conclusion, resistance-type exercise plus presleep protein ingestion increases overnight muscle connective tissue protein synthesis rates in older men. Exercise enhances the utilization of dietary protein-derived amino acids as precursors for de novo muscle connective tissue protein synthesis during overnight sleep.
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http://dx.doi.org/10.1123/ijsnem.2020-0222DOI Listing
February 2021

Comprehensive assessment of post-prandial protein handling by the application of intrinsically labelled protein in human subjects.

Proc Nutr Soc 2021 05 25;80(2):221-229. Epub 2021 Jan 25.

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, the Netherlands.

All human tissues are in a constant state of remodelling, regulated by the balance between tissue protein synthesis and breakdown rates. It has been well-established that protein ingestion stimulates skeletal muscle and whole-body protein synthesis. Stable isotope-labelled amino acid methodologies are commonly applied to assess the various aspects of protein metabolism in vivo in human subjects. However, to achieve a more comprehensive assessment of post-prandial protein handling in vivo in human subjects, intravenous stable isotope-labelled amino acid infusions can be combined with the ingestion of intrinsically labelled protein and the collection of blood and muscle tissue samples. The combined application of ingesting intrinsically labelled protein with continuous intravenous stable isotope-labelled amino acid infusion allows the simultaneous assessment of protein digestion and amino acid absorption kinetics (e.g. release of dietary protein-derived amino acids into the circulation), whole-body protein metabolism (whole-body protein synthesis, breakdown and oxidation rates and net protein balance) and skeletal muscle metabolism (muscle protein fractional synthesis rates and dietary protein-derived amino acid incorporation into muscle protein). The purpose of this review is to provide an overview of the various aspects of post-prandial protein handling and metabolism with a focus on insights obtained from studies that have applied intrinsically labelled protein under a variety of conditions in different populations.
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http://dx.doi.org/10.1017/S0029665120008034DOI Listing
May 2021

Intermittent versus continuous enteral nutrition attenuates increases in insulin and leptin during short-term bed rest.

Eur J Appl Physiol 2020 Sep 10;120(9):2083-2094. Epub 2020 Jul 10.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+), Maastricht, The Netherlands.

Purpose: To compare endocrine responses to intermittent vs continuous enteral nutrition provision during short-term bed rest.

Methods: Twenty healthy men underwent 7 days of bed rest, during which they were randomized to receive enteral nutrition (47%E as carbohydrate, 34%E as fat, 16%E as protein and 3%E as fibre) in a continuous (CONTINUOUS; n = 10; 24 h day at a constant rate) or intermittent (INTERMITTENT; n = 10; as 4 meals per day separated by 5 h) pattern. Daily plasma samples were taken every morning to assess metabolite/hormone concentrations.

Results: During bed rest, plasma leptin concentrations were elevated to a lesser extent with INTERMITTENT vs CONTINUOUS (iAUC: 0.42 ± 0.38 vs 0.95 ± 0.48 nmol L, respectively; P = 0.014) as were insulin concentrations (interaction effect, P < 0.001) which reached a peak of 369 ± 225 pmol L in CONTINUOUS, compared to 94 ± 38 pmol L in INTERMITTENT (P = 0.001). Changes in glucose infusion rate were positively correlated with changes in fasting plasma GLP-1 concentrations (r = 0.44, P = 0.049).

Conclusion: Intermittent enteral nutrition attenuates the progressive rise in plasma leptin and insulinemia seen with continuous feeding during bed rest, suggesting that continuous feeding increases insulin requirements to maintain euglycemia. This raises the possibility that hepatic insulin sensitivity is impaired to a greater extent with continuous versus intermittent feeding during bed rest. To attenuate endocrine and metabolic changes with enteral feeding, an intermittent feeding strategy may, therefore, be preferable to continuous provision of nutrition. This trial was registered on clinicaltrials.gov as NCT02521025.
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http://dx.doi.org/10.1007/s00421-020-04431-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7419443PMC
September 2020

Casein Ingestion Does Not Increase Muscle Connective Tissue Protein Synthesis Rates.

Med Sci Sports Exerc 2020 09;52(9):1983-1991

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, THE NETHERLANDS.

Purpose: This study aimed to assess the effect of dietary protein ingestion on intramuscular connective tissue protein synthesis rates during overnight recovery from a single bout of resistance exercise.

Methods: Thirty-six healthy, young males were randomly assigned to one of three treatments. One group ingested 30 g intrinsically L-[1-C]-phenylalanine-labeled casein protein before sleep (PRO, n = 12). The other two groups performed a bout of resistance exercise in the evening and ingested either placebo (EX, n = 12) or 30 g intrinsically L-[1-C]-phenylalanine-labeled casein protein before sleep (EX + PRO, n = 12). Continuous intravenous infusions of L-[ring-H5]-phenylalanine and L-[1-C]-leucine were applied, and blood and muscle tissue samples were collected to assess connective tissue protein synthesis rates and dietary protein-derived amino acid incorporation in the connective tissue protein fraction.

Results: Resistance exercise resulted in higher connective tissue protein synthesis rates when compared with rest (0.086 ± 0.017%·h [EX] and 0.080 ± 0.019%·h [EX + PRO] vs 0.059 ± 0.016%·h [PRO]; P < 0.05). Postexercise casein protein ingestion did not result in higher connective tissue protein synthesis rates when compared with postexercise placebo ingestion (P = 1.00). Dietary protein-derived amino acids were incorporated into the connective tissue protein fraction at rest, and to a greater extent during recovery from exercise (P = 0.002).

Conclusion: Resistance exercise increases intramuscular connective tissue protein synthesis rates during overnight sleep, with no further effect of postexercise protein ingestion. However, dietary protein-derived amino acids are being used as precursors to support de novo connective tissue protein synthesis.
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http://dx.doi.org/10.1249/MSS.0000000000002337DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7431152PMC
September 2020

Protein Type, Protein Dose, and Age Modulate Dietary Protein Digestion and Phenylalanine Absorption Kinetics and Plasma Phenylalanine Availability in Humans.

J Nutr 2020 08;150(8):2041-2050

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+), Maastricht, Netherlands.

Background: Dietary protein ingestion stimulates muscle protein synthesis by providing amino acids to the muscle. The magnitude and duration of the postprandial increase in muscle protein synthesis rates are largely determined by dietary protein digestion and amino acid absorption kinetics.

Objective: We assessed the impact of protein type, protein dose, and age on dietary protein digestion and amino acid absorption kinetics in vivo in humans.

Methods: We included data from 18 randomized controlled trials with a total of 602 participants [age: 53 ± 23 y; BMI (kg/m2): 24.8 ± 3.3] who consumed various quantities of intrinsically l-[1-13C]-phenylalanine-labeled whey (n = 137), casein (n = 393), or milk (n = 72) protein and received intravenous infusions of l-[ring-2H5]-phenylalanine, which allowed us to assess protein digestion and phenylalanine absorption kinetics and the postprandial release of dietary protein-derived phenylalanine into the circulation. The effect of aging on these processes was assessed in a subset of 82 young (aged 22 ± 3 y) and 83 older (aged 71 ± 5 y) individuals.

Results: A total of 50% ± 14% of dietary protein-derived phenylalanine appeared in the circulation over a 5-h postprandial period. Casein ingestion resulted in a smaller (45% ± 11%), whey protein ingestion in an intermediate (57% ± 10%), and milk protein ingestion in a greater (65% ± 13%) fraction of dietary protein-derived phenylalanine appearing in the circulation (P < 0.001). The postprandial availability of dietary protein-derived phenylalanine in the circulation increased with the ingestion of greater protein doses (P < 0.05). Protein digestion and phenylalanine absorption kinetics were attenuated in older when compared with young individuals, with 45% ± 10% vs. 51% ± 14% of dietary protein-derived phenylalanine appearing in the circulation, respectively (P = 0.001).

Conclusions: Protein type, protein dose, and age modulate dietary protein digestion and amino acid absorption kinetics and subsequent postprandial plasma amino acid availability in vivo in humans. These trials were registered at clinicaltrials.gov as NCT00557388, NCT00936039, NCT00991523, NCT01317511, NCT01473576, NCT01576848, NCT01578590, NCT01615276, NCT01680146, NCT01820975, NCT01986842, and NCT02596542, and at http://www.trialregister.nl as NTR3638, NTR3885, NTR4060, NTR4429, and NTR4492.
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http://dx.doi.org/10.1093/jn/nxaa024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7398787PMC
August 2020

Endurance-Type Exercise Increases Bulk and Individual Mitochondrial Protein Synthesis Rates in Rats.

Int J Sport Nutr Exerc Metab 2020 Feb 7:1-12. Epub 2020 Feb 7.

Maastricht University.

Physical activity increases muscle protein synthesis rates. However, the impact of exercise on the coordinated up- and/or downregulation of individual protein synthesis rates in skeletal muscle tissue remains unclear. The authors assessed the impact of exercise on mixed muscle, myofibrillar, and mitochondrial protein synthesis rates as well as individual protein synthesis rates in vivo in rats. Adult Lewis rats either remained sedentary (n = 3) or had access to a running wheel (n = 3) for the last 2 weeks of a 3-week experimental period. Deuterated water was injected and subsequently administered in drinking water over the experimental period. Blood and soleus muscle were collected and used to assess bulk mixed muscle, myofibrillar, and mitochondrial protein synthesis rates using gas chromatography-mass spectrometry and individual muscle protein synthesis rates using liquid chromatography-mass spectrometry (i.e., dynamic proteomic profiling). Wheel running resulted in greater myofibrillar (3.94 ± 0.26 vs. 3.03 ± 0.15%/day; p < .01) and mitochondrial (4.64 ± 0.24 vs. 3.97 ± 0.26%/day; p < .05), but not mixed muscle (2.64 ± 0.96 vs. 2.38 ± 0.62%/day; p = .71) protein synthesis rates, when compared with the sedentary condition. Exercise impacted the synthesis rates of 80 proteins, with the difference from the sedentary condition ranging between -64% and +420%. Significantly greater synthesis rates were detected for F1-ATP synthase, ATP synthase subunit alpha, hemoglobin, myosin light chain-6, and synaptopodin-2 (p < .05). The skeletal muscle protein adaptive response to endurance-type exercise involves upregulation of mitochondrial protein synthesis rates, but it is highly coordinated as reflected by the up- and downregulation of various individual proteins across different bulk subcellular protein fractions.
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http://dx.doi.org/10.1123/ijsnem.2019-0281DOI Listing
February 2020

Short-term muscle disuse induces a rapid and sustained decline in daily myofibrillar protein synthesis rates.

Am J Physiol Endocrinol Metab 2020 02 19;318(2):E117-E130. Epub 2019 Nov 19.

Department of Sport and Health Sciences, College of Life and Environmental Science, University of Exeter, Exeter, United Kingdom.

Short-term muscle disuse has been reported to lower both postabsorptive and postprandial myofibrillar protein synthesis rates. This study assessed the impact of disuse on daily myofibrillar protein synthesis rates following short-term (2 and 7 days) muscle disuse under free living conditions. Thirteen healthy young men (age: 20 ± 1 yr; BMI: 23 ± 1 kg/m) underwent 7 days of unilateral leg immobilization via a knee brace, with the nonimmobilized leg acting as a control. Four days before immobilization participants ingested 400 mL of 70% deuterated water, with 50-mL doses consumed daily thereafter. Upper leg bilateral MRI scans and muscle biopsies were collected before and after 2 and 7 days of immobilization to determine quadriceps volume and daily myofibrillar protein synthesis rates. Immobilization reduced quadriceps volume in the immobilized leg by 1.7 ± 0.3 and 6.7 ± 0.6% after 2 and 7 days, respectively, with no changes in the control leg. Over the 1-wk immobilization period, myofibrillar protein synthesis rates were 36 ± 4% lower in the immobilized (0.81 ± 0.04%/day) compared with the control (1.26 ± 0.04%/day) leg ( < 0.001). Myofibrillar protein synthesis rates in the control leg did not change over time ( = 0.775), but in the immobilized leg they were numerically lower during the 0- to 2-day period (16 ± 6%, 1.11 ± 0.09%/day, = 0.153) and were significantly lower during the 2- to 7-day period (44 ± 5%, 0.70 ± 0.06%/day, < 0.001) when compared with the control leg. We conclude that 1 wk of muscle disuse induces a rapid and sustained decline in daily myofibrillar protein synthesis rates in healthy young men.
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http://dx.doi.org/10.1152/ajpendo.00360.2019DOI Listing
February 2020

Time-dependent regulation of postprandial muscle protein synthesis rates after milk protein ingestion in young men.

J Appl Physiol (1985) 2019 12 14;127(6):1792-1801. Epub 2019 Nov 14.

Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, Illinois.

The anabolic action of "fast" whey protein on the regulation of postprandial muscle protein synthesis has been established to be short-lived in healthy young adults. We assessed the time course of anabolic signaling activation and stimulation of myofibrillar protein synthesis rates (MPS) after ingestion of a food source that represents a more typical meal-induced pattern of aminoacidemia. Seven young men (age: 22 ± 1 y) underwent repeated blood and biopsy sampling during primed, continuous l-[-H]phenylalanine and l-[1-C]leucine tracer infusions and ingested 38 g of l-[1-C]phenylalanine- and l-[1-C]leucine-labeled milk protein concentrate. A total of ∼27 ± 4 (∼10 g) and ∼31 ± 1% (∼12 g) of dietary protein-derived amino acids were released in circulation between 0 and 120 min and 120-300 min, respectively, of the postprandial period. l-[-H]phenylalanine-based MPS increased above basal (0.025 ± 0.008%/h) by ∼75% (0.043 ± 0.009%/h; = 0.05) between 0 and 120 min and by ∼86% (0.046 ± 0.004%/h; = 0.02) between 120 and 300 min, respectively. l-[1-C]leucine-based MPS increased above basal (0.027 ± 0.002%/h) by ∼72% (0.051 ± 0.016%/h; = 0.10) between 0 and 120 min and by ∼62% (0.047 ± 0.004%/h; = 0.001) between 120 and 300 min, respectively. Myofibrillar protein-bound l-[1-C]phenylalanine increased over time ( < 0.001) and equaled 0.004 ± 0.001, 0.008 ± 0.002, 0.017 ± 0.004, and 0.020 ± 0.003 mole percent excess at 60, 120, 180, and 300 min, respectively, of the postprandial period. Milk protein ingestion increased mTORC1 phosphorylation at 120, 180, and 300 min of the postprandial period (all < 0.05). Our results show that ingestion of 38 g of milk protein results in sustained increases in MPS throughout a 5-h postprandial period in healthy young men. The stimulation of muscle protein synthesis after whey protein ingestion is short-lived due to its transient systemic appearance of amino acids. Our study characterized the muscle anabolic response to a protein source that results in a more gradual release of amino acids into circulation. Our work demonstrates that a sustained increase in postprandial plasma amino acid availability after milk protein ingestion results in a prolonged stimulation of muscle protein synthesis rates in healthy young men.
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http://dx.doi.org/10.1152/japplphysiol.00608.2019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054632PMC
December 2019

The intrinsically labeled protein approach is the preferred method to quantify the release of dietary protein-derived amino acids into the circulation.

Am J Physiol Endocrinol Metab 2019 09;317(3):E433-E434

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.

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http://dx.doi.org/10.1152/ajpendo.00155.2019DOI Listing
September 2019

Branched-chain amino acid and branched-chain ketoacid ingestion increases muscle protein synthesis rates in vivo in older adults: a double-blind, randomized trial.

Am J Clin Nutr 2019 10;110(4):862-872

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht, Netherlands.

Background: Protein ingestion increases muscle protein synthesis rates. However, limited data are currently available on the effects of branched-chain amino acid (BCAA) and branched-chain ketoacid (BCKA) ingestion on postprandial muscle protein synthesis rates.

Objective: The aim of this study was to compare the impact of ingesting 6 g BCAA, 6 g BCKA, and 30 g milk protein (MILK) on the postprandial rise in circulating amino acid concentrations and subsequent myofibrillar protein synthesis rates in older males.

Methods: In a parallel design, 45 older males (age: 71 ± 1 y; BMI: 25.4 ± 0.8 kg/m2) were randomly assigned to ingest a drink containing 6 g BCAA, 6 g BCKA, or 30 g MILK. Basal and postprandial myofibrillar protein synthesis rates were assessed by primed continuous l-[ring-13C6]phenylalanine infusions with the collection of blood samples and muscle biopsies.

Results: Plasma BCAA concentrations increased following test drink ingestion in all groups, with greater increases in the BCAA and MILK groups compared with the BCKA group (P < 0.05). Plasma BCKA concentrations increased following test drink ingestion in all groups, with greater increases in the BCKA group compared with the BCAA and MILK groups (P < 0.05). Ingestion of MILK, BCAA, and BCKA significantly increased early myofibrillar protein synthesis rates (0-2 h) above basal rates (from 0.020 ± 0.002%/h to 0.042 ± 0.004%/h, 0.022 ± 0.002%/h to 0.044 ± 0.004%/h, and 0.023 ± 0.003%/h to 0.044 ± 0.004%/h, respectively; P < 0.001), with no differences between groups (P > 0.05). Myofibrillar protein synthesis rates during the late postprandial phase (2-5 h) remained elevated in the MILK group (0.039 ± 0.004%/h; P < 0.001), but returned to baseline values following BCAA and BCKA ingestion (0.024 ± 0.005%/h and 0.024 ± 0.005%/h, respectively; P > 0.05).

Conclusions: Ingestion of 6 g BCAA, 6 g BCKA, and 30 g MILK increases myofibrillar protein synthesis rates during the early postprandial phase (0-2 h) in vivo in healthy older males. The postprandial increase following the ingestion of 6 g BCAA and BCKA is short-lived, with higher myofibrillar protein synthesis rates only being maintained following the ingestion of an equivalent amount of intact milk protein. This trial was registered at Nederlands Trial Register (www.trialregister.nl) as NTR6047.
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http://dx.doi.org/10.1093/ajcn/nqz120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6766442PMC
October 2019

Leucine coingestion augments the muscle protein synthetic response to the ingestion of 15 g of protein following resistance exercise in older men.

Am J Physiol Endocrinol Metab 2019 09 21;317(3):E473-E482. Epub 2019 May 21.

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.

Older adults have shown an attenuated postexercise increase in muscle protein synthesis rates following ingestion of smaller amounts of protein compared with younger adults. Consequently, it has been suggested that older adults require the ingestion of more protein to increase postexercise muscle protein synthesis rates compared with younger adults. We investigated whether coingestion of 1.5 g of free leucine with a single 15-g bolus of protein further augments the postprandial muscle protein synthetic response during recovery from resistance-type exercise in older men. Twenty-four healthy older men (67 ± 1 yr) were randomly assigned to ingest 15 g of milk protein concentrate (MPC80) with (15G+LEU; = 12) or without (15G; = 12) 1.5 g of free leucine after performing a single bout of resistance-type exercise. Postprandial protein digestion and amino acid absorption kinetics, whole body protein metabolism, and postprandial myofibrillar protein synthesis rates were assessed using primed, continuous infusions with l-[-H]phenylalanine, l-[-H]tyrosine, and l-[1-C]leucine combined with ingestion of intrinsically l-[1-C]phenylalanine-labeled milk protein. A total of 70 ± 1% (10.5 ±0.2 g) and 75 ± 2% (11.2 ± 0.3 g) of the protein-derived amino acids were released in the circulation during the 6-h postexercise recovery phase in 15G+LEU and 15G, respectively ( < 0.05). Postexercise myofibrillar protein synthesis rates were 16% (0.058 ± 0.003 vs. 0.049 ± 0.002%/h, < 0.05; based on l-[-H]phenylalanine) and 19% (0.071 ± 0.003 vs. 0.060 ± 0.003%/h, < 0.05; based on l-[1-C]leucine) greater in 15G+LEU compared with 15G. Leucine coingestion further augments the postexercise muscle protein synthetic response to the ingestion of a single 15-g bolus of protein in older men.
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http://dx.doi.org/10.1152/ajpendo.00073.2019DOI Listing
September 2019

One Week of Step Reduction Lowers Myofibrillar Protein Synthesis Rates in Young Men.

Med Sci Sports Exerc 2019 10;51(10):2125-2134

School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UNITED KINGDOM.

Purpose: Across the lifespan, physical activity levels decrease and time spent sedentary typically increases. However, little is known about the impact that these behavioral changes have on skeletal muscle mass regulation. The primary aim of this study was to use a step reduction model to determine the impact of reduced physical activity and increased sedentary time on daily myofibrillar protein synthesis rates in healthy young men.

Methods: Eleven men (22 ± 2 yr) completed 7 d of habitual physical activity (HPA) followed by 7 d of step reduction (SR). Myofibrillar protein synthesis rates were determined during HPA and SR using the deuterated water (H2O) method combined with the collection of skeletal muscle biopsies and daily saliva samples. Gene expression of selected proteins related to muscle mass regulation and oxidative metabolism were determined via real time reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

Results: Daily step count was reduced by approximately 91% during SR (from 13,054 ± 2763 steps per day to 1192 ± 330 steps per day; P < 0.001) and this led to an increased contribution of sedentary time to daily activity (73% ± 6% to 90% ± 3%; P < 0.001). Daily myofibrillar protein synthesis decreased by approximately 27% from 1.39 ± 0.32%·d during HPA to 1.01 ± 0.38%·d during SR (P < 0.05). Muscle atrophy F-box and myostatin mRNA expression were upregulated, whereas mechanistic target of rapamycin, p53, and PDK4 mRNA expression were downregulated after SR (P < 0.05).

Conclusions: One week of reduced physical activity and increased sedentary time substantially lowers daily myofibrillar protein synthesis rates in healthy young men.
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http://dx.doi.org/10.1249/MSS.0000000000002034DOI Listing
October 2019

The Impact of Pre-sleep Protein Ingestion on the Skeletal Muscle Adaptive Response to Exercise in Humans: An Update.

Front Nutr 2019 6;6:17. Epub 2019 Mar 6.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre (MUMC+), Maastricht, Netherlands.

This review provides an update on recent research assessing the effect of pre-sleep protein ingestion on muscle protein synthesis rates during overnight sleep and the skeletal muscle adaptive response to exercise training. Protein ingested prior to sleep is effectively digested and absorbed during overnight sleep, thereby increasing overnight muscle protein synthesis rates. Protein consumption prior to sleep does not appear to reduce appetite during breakfast the following day and does not change resting energy expenditure. When applied over a prolonged period of resistance-type exercise training, pre-sleep protein supplementation has a beneficial effect on the increase in muscle mass and strength. Protein ingestion before sleep is hypothesized to represent an effective nutritional strategy to preserve muscle mass in the elderly, especially when combined with physical activity or muscle contraction by means of neuromuscular electrical stimulation. In conclusion, protein ingestion prior to sleep is an effective interventional strategy to increase muscle protein synthesis rates during overnight sleep and can be applied to support the skeletal muscle adaptive response to resistance-type exercise training.
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http://dx.doi.org/10.3389/fnut.2019.00017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6415027PMC
March 2019

Dose-Dependent Increases in Whole-Body Net Protein Balance and Dietary Protein-Derived Amino Acid Incorporation into Myofibrillar Protein During Recovery from Resistance Exercise in Older Men.

J Nutr 2019 02;149(2):221-230

NUTRIM School of Nutrition and Translational Research in Metabolism.

Background: Age-related decline in skeletal muscle mass is at least partly attributed to anabolic resistance to food intake. Resistance exercise sensitizes skeletal muscle tissue to the anabolic properties of amino acids.

Objective: The present study assessed protein digestion and amino acid absorption kinetics, whole-body protein balance, and the myofibrillar protein synthetic response to ingestion of different amounts of protein during recovery from resistance exercise in older men.

Methods: Forty-eight healthy older men [mean ± SEM age: 66 ± 1 y; body mass index (kg/m2): 25.4 ± 0.3] were randomly assigned to ingest 0, 15, 30, or 45 g milk protein concentrate after a single bout of resistance exercise consisting of 4 sets of 10 repetitions of leg press and leg extension and 2 sets of 10 repetitions of lateral pulldown and chest press performed at 75-80% 1-repetition maximum. Postprandial protein digestion and amino acid absorption kinetics, whole-body protein metabolism, and myofibrillar protein synthesis rates were assessed using primed, continuous infusions of l-[ring-2H5]-phenylalanine, l-[ring-2H2]-tyrosine, and l-[1-13C]-leucine combined with ingestion of intrinsically l-[1-13C]-phenylalanine and l-[1-13C]-leucine labeled protein.

Results: Whole-body net protein balance showed a dose-dependent increase after ingestion of 0, 15, 30, or 45 g of protein (0.015 ± 0.002, 0.108 ± 0.004, 0.162 ± 0.008, and 0.215 ± 0.009 μmol Phe · kg-1 · min-1, respectively; P < 0.001). Myofibrillar protein synthesis rates were higher after ingesting 30 (0.0951% ± 0.0062%/h, P = 0.07) or 45 g of protein (0.0970% ± 0.0062%/h, P < 0.05) than after 0 g (0.0746% ± 0.0051%/h). Incorporation of dietary protein-derived amino acids (l-[1-13C]-phenylalanine) into de novo myofibrillar protein showed a dose-dependent increase after ingestion of 15, 30, or 45 g protein (0.0171 ± 0.0017, 0.0296 ± 0.0030, and 0.0397 ± 0.0026 mole percentage excess, respectively; P < 0.05).

Conclusions: Dietary protein ingested during recovery from resistance exercise is rapidly digested and absorbed. Whole-body net protein balance and dietary protein-derived amino acid incorporation into myofibrillar protein show dose-dependent increases. Ingestion of ≥30 g protein increases postexercise myofibrillar protein synthesis rates in older men. This trial was registered at Nederlands Trial Register as NTR4492.
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http://dx.doi.org/10.1093/jn/nxy263DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6374151PMC
February 2019

Dietary feeding pattern does not modulate the loss of muscle mass or the decline in metabolic health during short-term bed rest.

Am J Physiol Endocrinol Metab 2019 03 15;316(3):E536-E545. Epub 2019 Jan 15.

Department of Human Biology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ , The Netherlands.

Short periods of bed rest lead to the loss of muscle mass and quality. It has been speculated that dietary feeding pattern may have an impact upon muscle protein synthesis rates and, therefore, modulate the loss of muscle mass and quality. We subjected 20 healthy men (age: 25 ± 1 yr, body mass index: 23.8 ± 0.8 kg/m) to 1 wk of strict bed rest with intermittent (4 meals/day) or continuous (24 h/day) enteral tube feeding. Participants consumed deuterium oxide for 7 days before bed rest and throughout the 7-day bed rest period. Prior to and immediately after bed rest, lean body mass (dual energy X-ray absorptiometry), quadriceps cross-sectional area (CSA; CT), maximal oxygen uptake capacity (V̇o), and whole body insulin sensitivity (hyperinsulinemic-euglycemic clamp) were assessed. Muscle biopsies were collected 7 days before, 1 day before, and immediately after bed rest to assess muscle tracer incorporation. Bed rest resulted in 0.3 ± 0.3 vs. 0.7 ± 0.4 kg lean tissue loss and a 1.1 ± 0.6 vs. 0.8 ± 0.5% decline in quadriceps CSA in the intermittent vs. continuous feeding group, respectively (both P < 0.05), with no differences between groups (both P > 0.05). Moreover, feeding pattern did not modulate the bed rest-induced decline in insulin sensitivity (-46 ± 3% vs. 39 ± 3%; P < 0.001) or V̇o (-2.5 ± 2.2 vs. -8.6 ± 2.2%; P < 0.010) (both P > 0.05). Myofibrillar protein synthesis rates during bed rest did not differ between the intermittent and continuous feeding group (1.33 ± 0.07 vs. 1.50 ± 0.13%/day, respectively; P > 0.05). In conclusion, dietary feeding pattern does not modulate the loss of muscle mass or the decline in metabolic health during 1 wk of bed rest in healthy men.
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http://dx.doi.org/10.1152/ajpendo.00378.2018DOI Listing
March 2019

Protein Supplementation after Exercise and before Sleep Does Not Further Augment Muscle Mass and Strength Gains during Resistance Exercise Training in Active Older Men.

J Nutr 2018 11;148(11):1723-1732

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Center+, Maastricht, Netherlands.

Background: The proposed benefits of protein supplementation on the skeletal muscle adaptive response to resistance exercise training in older adults remain unclear.

Objective: The present study assessed whether protein supplementation after exercise and before sleep augments muscle mass and strength gains during resistance exercise training in older individuals.

Methods: Forty-one older men [mean ± SEM age: 70 ± 1 y; body mass index (kg/m2): 25.3 ± 0.4] completed 12 wk of whole-body resistance exercise training (3 sessions/wk) and were randomly assigned to ingest either protein (21 g protein, 3 g total leucine, 9 g carbohydrate, 3 g fat; n = 21) or an energy-matched placebo (0 g protein, 25 g carbohydrate, 6 g fat; n = 20) after exercise and each night before sleep. Maximal strength was assessed by 1-repetition-maximum (1RM) strength testing, and muscle hypertrophy was assessed at the whole-body (dual-energy X-ray absorptiometry), upper leg (computed tomography scan), and muscle fiber (biopsy) levels. Muscle protein synthesis rates were assessed during week 12 of training with the use of deuterated water (2H2O) administration.

Results: Leg-extension 1RM increased in both groups (placebo: 88 ± 3 to 104 ± 4 kg; protein: 85 ± 3 to 102 ± 4 kg; P < 0.001), with no differences between groups. Quadriceps cross-sectional area (placebo: 67.8 ± 1.7 to 73.5 ± 2.0 cm2; protein: 68.4 ± 1.4 to 72.3 ± 1.4 cm2; P < 0.001) increased in both groups, with no differences between groups. Muscle fiber hypertrophy occurred in type II muscle fibers (placebo: 5486 ± 418 to 6492 ± 429 µm2; protein: 5367 ± 301 to 6259 ± 391 µm2; P < 0.001), with no differences between groups. Muscle protein synthesis rates were 1.62% ± 0.06% and 1.57% ± 0.05%/d in the placebo and protein groups, respectively, with no differences between groups.

Conclusion: Protein supplementation after exercise and before sleep does not further augment skeletal muscle mass or strength gains during resistance exercise training in active older men. This study was registered at the Netherlands Trial Registry (www.trialregister.nl) as NTR5082.
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http://dx.doi.org/10.1093/jn/nxy169DOI Listing
November 2018

Skeletal muscle fiber characteristics in patients with chronic heart failure: impact of disease severity and relation with muscle oxygenation during exercise.

J Appl Physiol (1985) 2018 08 9. Epub 2018 Aug 9.

Cardiology, Máxima Medical Centre, Netherlands.

Introduction: Skeletal muscle function in patients with heart failure and reduced ejection fraction (HFrEF) greatly determines exercise capacity. However, reports on skeletal muscle fiber dimensions, fiber capillarization, and their physiological importance are inconsistent.

Methods: Twenty-five moderately-impaired patients with HFrEF and 25 healthy control (HC) subjects underwent muscle biopsy sampling. Type I and type II muscle fiber characteristics were determined by immunohistochemistry. In patients with HFrEF, enzymatic oxidative capacity was assessed, and pulmonary oxygen uptake (VO) and skeletal muscle oxygenation during maximal and moderate-intensity exercise were measured using near-infrared spectroscopy.

Results: While muscle fiber cross-sectional area (CSA) was not different between patients with HFrEF and HC, percentage of type I fibers was higher in HC (46±15% versus 37±12%, respectively, P=0.041). Fiber type distribution and CSA were not different between patients in New York Heart Association (NYHA) class II and III. Type I muscle fiber capillarization was higher in HFrEF compared with controls (capillary-to-fiber perimeter exchange (CFPE) index: 5.70±0.92 versus 5.05±0.82, respectively, P=0.027). Patients in NYHA class III had slower VO and muscle deoxygenation kinetics during onset of exercise, and lower muscle oxidative capacity than those in class II (P<0.05). Also, fiber capillarization was lower, but not compared with HC. Higher CFPE index was related to faster deoxygenation (r=-0.682, P=0.001), however, not to muscle oxidative capacity (r=-0.282, P=0.216).

Conclusions: Type I muscle fiber capillarization is higher in HFrEF compared with HC, but not in patients with greater exercise impairment. Greater capillarization may positively affect VO kinetics by enhancing muscle oxygen diffusion.
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http://dx.doi.org/10.1152/japplphysiol.00057.2018DOI Listing
August 2018

Age-Associated Impairments in Mitochondrial ADP Sensitivity Contribute to Redox Stress in Senescent Human Skeletal Muscle.

Cell Rep 2018 03;22(11):2837-2848

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, 6200 Maastricht, the Netherlands.

It remains unknown if mitochondrial bioenergetics are altered with aging in humans. We established an in vitro method to simultaneously determine mitochondrial respiration and HO emission in skeletal muscle tissue across a range of biologically relevant ADP concentrations. Using this approach, we provide evidence that, although the capacity for mitochondrial HO emission is not increased with aging, mitochondrial ADP sensitivity is impaired. This resulted in an increase in mitochondrial HO and the fraction of electron leak to HO, in the presence of virtually all ADP concentrations examined. Moreover, although prolonged resistance training in older individuals increased muscle mass, strength, and maximal mitochondrial respiration, exercise training did not alter HO emission rates in the presence of ADP, the fraction of electron leak to HO, or the redox state of the muscle. These data establish that a reduction in mitochondrial ADP sensitivity increases mitochondrial HO emission and contributes to age-associated redox stress.
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http://dx.doi.org/10.1016/j.celrep.2018.02.069DOI Listing
March 2018

Daily resistance-type exercise stimulates muscle protein synthesis in vivo in young men.

J Appl Physiol (1985) 2018 01 21;124(1):66-75. Epub 2017 Sep 21.

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+) , Maastricht , The Netherlands.

Resistance-type exercise increases muscle protein synthesis rates during acute postexercise recovery. The impact of resistance-type exercise training on (local) muscle protein synthesis rates under free-living conditions on a day-to-day basis remains unclear. We determined the impact of daily unilateral resistance-type exercise on local myofibrillar protein synthesis rates during a 3-day period. Twelve healthy young men (22 ± 1 yr) were recruited to participate in this study where they performed daily, unilateral resistance-type exercise during a 3-day intervention period. Two days before the exercise training subjects ingested 400 ml deuterated water (HO). Additional 50-ml doses of deuterated water were ingested daily during the training period. Saliva and blood samples were collected daily to assess body water and amino acid precursor deuterium enrichments, respectively. Muscle tissue biopsies were collected before and after the 3 days of unilateral resistance-type exercise training from both the exercised and the nonexercised, control leg for the assessment of muscle protein synthesis rates. Deuterated water dosing resulted in a steady-state body water enrichment of 0.70 ± 0.03%. Intramuscular free [H]alanine enrichment increased up to 1.84 ± 0.06 mole percent excess (MPE) before the exercise training and did not change in both the exercised and control leg during the 3 subsequent exercise training days (2.11 ± 0.11 and 2.19 ± 0.12 MPE, respectively; P > 0.05). Muscle protein synthesis rates averaged 1.984 ± 0.118 and 1.642 ± 0.089%/day in the exercised vs. nonexercised, control leg when assessed over the entire 3-day period ( P < 0.05). Daily resistance-type exercise stimulates (local) muscle protein synthesis in vivo in humans. NEW & NOTEWORTHY This study demonstrates that daily resistance-type exercise stimulates muscle protein synthesis rates in vivo in humans over multiple days. Whereas acute studies have shown that resistance-type exercise increases muscle protein synthesis rates by 50-100%, we observed a lower impact of resistance-type exercise under free-living conditions. We also compared precursor tracer selection for the calculation of muscle protein synthesis rates and observed that saliva deuterium enrichment serves as an appropriate and practical choice of precursor.
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http://dx.doi.org/10.1152/japplphysiol.00610.2017DOI Listing
January 2018

Protein Ingestion before Sleep Increases Overnight Muscle Protein Synthesis Rates in Healthy Older Men: A Randomized Controlled Trial.

J Nutr 2017 12 30;147(12):2252-2261. Epub 2017 Aug 30.

NUTRIM, School of Nutrition and Translational Research in Metabolism, and

The loss of skeletal muscle mass with aging has been attributed to the blunted anabolic response to protein intake. Presleep protein ingestion has been suggested as an effective strategy to compensate for such anabolic resistance. We assessed the efficacy of presleep protein ingestion on dietary protein digestion and absorption kinetics and overnight muscle protein synthesis rates in older men. In a randomized, double-blind, parallel design, 48 older men (mean ± SEM age: 72 ± 1 y) ingested 40 g casein (PRO40), 20 g casein (PRO20), 20 g casein plus 1.5 g leucine (PRO20+LEU), or a placebo before sleep. Ingestion of intrinsically l-[1-C]-phenylalanine- and l-[1-C]-leucine-labeled protein was combined with intravenous l-[ring-H]-phenylalanine and l-[1-C]-leucine infusions during sleep. Muscle and blood samples were collected throughout overnight sleep. Exogenous phenylalanine appearance rates increased after protein ingestion, but to a greater extent in PRO40 than in PRO20 and PRO20+LEU ( < 0.05). Overnight myofibrillar protein synthesis rates (based on l-[ring-H]-phenylalanine) were 0.033% ± 0.002%/h, 0.037% ± 0.003%/h, 0.039% ± 0.002%/h, and 0.044% ± 0.003%/h in placebo, PRO20, PRO20+LEU, and PRO40, respectively, and were higher in PRO40 than in placebo ( = 0.02). Observations were similar based on l-[1-C]-leucine tracer (placebo: 0.047% ± 0.004%/h and PRO40: 0.058% ± 0.003%/h, = 0.08). More protein-derived amino acids (l-[1-C]-phenylalanine) were incorporated into myofibrillar protein in PRO40 than in PRO20 (0.033 ± 0.002 and 0.019 ± 0.002 MPE, respectively, < 0.001) and tended to be higher than in PRO20+LEU (0.025 ± 0.002 MPE, = 0.06). Protein ingested before sleep is properly digested and absorbed throughout the night, providing precursors for myofibrillar protein synthesis during sleep in healthy older men. Ingestion of 40 g protein before sleep increases myofibrillar protein synthesis rates during overnight sleep. These findings provide the scientific basis for a novel nutritional strategy to support muscle mass preservation in aging and disease. This trial was registered at www.trialregister.nl as NTR3885.
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http://dx.doi.org/10.3945/jn.117.254532DOI Listing
December 2017

Presleep dietary protein-derived amino acids are incorporated in myofibrillar protein during postexercise overnight recovery.

Am J Physiol Endocrinol Metab 2018 05 23;314(5):E457-E467. Epub 2017 May 23.

NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre , Maastricht , The Netherlands.

The purpose of this study was to determine the impact of ingesting 30 g casein protein with and without 2 g free leucine before sleep on myofibrillar protein synthesis rates during postexercise overnight recovery. Thirty-six healthy young men performed a single bout of resistance-type exercise in the evening (1945) after a full day of dietary standardization. Thirty minutes before sleep (2330), subjects ingested 30 g intrinsically l-[1-C]phenylalanine-labeled protein with (PRO+leu, n = 12) or without (PRO, n = 12) 2 g free leucine, or a noncaloric placebo (PLA, n = 12). Continuous intravenous l-[ ring-H]phenylalanine, l-[1-C]leucine, and l-[ ring-H]tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole body protein net balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into myofibrillar protein. Protein ingestion before sleep improved overnight whole body protein net balance ( P < 0.001). Myofibrillar protein synthesis rates did not differ significantly between treatments as assessed by l-[ ring-H]phenylalanine (0.057 ± 0.002, 0.055 ± 0.002, and 0.055 ± 0.004%/h for PLA, PRO, and PRO+leu, respectively; means ± SE; P = 0.850) or l-[1-C]leucine (0.080 ± 0.004, 0.073 ± 0.004, and 0.083 ± 0.006%/h, respectively; P = 0.328). Myofibrillar l-[1-C]phenylalanine enrichments increased following protein ingestion but did not differ between the PRO and PRO+leu treatments. In conclusion, protein ingestion before sleep improves whole body protein net balance and provides amino acids that are incorporated into myofibrillar protein during sleep. However, the ingestion of 30 g casein protein with or without additional free leucine before sleep does not increase muscle protein synthesis rates during postexercise overnight recovery.
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http://dx.doi.org/10.1152/ajpendo.00273.2016DOI Listing
May 2018

Food ingestion in an upright sitting position increases postprandial amino acid availability when compared with food ingestion in a lying down position.

Appl Physiol Nutr Metab 2017 Jul 17;42(7):738-743. Epub 2017 Feb 17.

a Department of Human Biology and Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Center+, P.O. Box 616, 6200 MD Maastricht, the Netherlands.

Dietary protein digestion and absorption kinetics determine the postprandial increase in muscle protein synthesis. We recently demonstrated that body position during feeding can modulate the postprandial rise in plasma amino acid availability. Here we investigated whether protein ingestion in an upright sitting body position accelerates gastric emptying and improves dietary protein digestion and subsequent amino acid absorption compared with feeding in a supine lying body position. In a crossover design, 8 young males (age, 26 ± 1 years; body mass index, 24.0 ± 0.9 kg·m) ingested 20 g intrinsically l-[1-C]-phenylalanine-labeled milk protein plus 1.5 g paracetamol while sitting in an upright position or lying down in a supine position. Blood samples were collected frequently during a 5-h postprandial period. Gastric emptying rates and dietary protein digestion and absorption were assessed using plasma paracetamol and amino acid concentrations as well as plasma l-[1-C]-phenylalanine enrichments. Peak plasma leucine concentrations were higher when protein was ingested in an upright sitting versus lying position (213 ± 15 vs 193 ± 12 μmol·L, P < 0.05), which was accompanied by a trend for a greater overall leucine response (13 989 ± 720 vs 11 875 ± 1073 AU, respectively; P = 0.05). Peak plasma paracetamol concentrations were higher in the sitting versus lying treatment (11.6 ± 0.5 vs 9.3 ± 0.6 mg·L, P < 0.05). Protein ingestion in an upright sitting position accelerates gastric emptying and increases the postprandial rise in plasma amino acid availability by increasing protein digestion and amino acid absorption rates. Therefore, feeding in an upright body position as opposed to a lying position is an important prerequisite to allow proper postprandial muscle protein accretion.
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http://dx.doi.org/10.1139/apnm-2016-0522DOI Listing
July 2017

Resistance Exercise Augments Postprandial Overnight Muscle Protein Synthesis Rates.

Med Sci Sports Exerc 2016 12;48(12):2517-2525

1NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, THE NETHERLANDS; 2Top Institute Food and Nutrition (TIFN), Wageningen, THE NETHERLANDS; 3AIS Physiology, Australian Institute of Sport, Belconnen, AUSTRALIA; and 4Gatorade Sports Science Institute, Leicester, UNITED KINGDOM.

Introduction: We have previously shown that protein ingestion before sleep increases overnight muscle protein synthesis rates. Whether prior exercise further augments the muscle protein synthetic response to presleep protein ingestion remains to be established.

Objective: This study aimed to assess whether resistance-type exercise performed in the evening increases the overnight muscle protein synthetic response to presleep protein ingestion.

Methods: Twenty-four healthy young men were randomly assigned to ingest 30 g intrinsically L-[1-C]-phenylalanine and L-[1-C]-leucine-labeled casein protein before going to sleep with (PRO + EX, n = 12) or without (PRO, n = 12) prior resistance-type exercise performed in the evening. Continuous intravenous L-[ring-H5]-phenylalanine, L-[1-C]-leucine, and L-[ring-H2]-tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole-body protein balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into de novo myofibrillar protein.

Results: A total of 57% ± 1% of the ingested protein-derived phenylalanine appeared in the circulation during overnight sleep. Overnight myofibrillar protein synthesis rates were 37% (0.055%·h ± 0.002%·h vs. 0.040%·h ± 0.003%·h, P < 0.001, based on L-[ring- H5]-phenylalanine) and 31% (0.073%·h ± 0.004%·h vs. 0.055%·h ± 0.006%·h, P = 0.024, based on L-[1-C]-leucine) higher in PRO + EX compared with PRO. Substantially more of the dietary protein-derived amino acids were incorporated into de novo myofibrillar protein during overnight sleep in PRO + EX compared with PRO (0.026 ± 0.003 vs. 0.015 ± 0.003 molar percent excess, P = 0.012).

Conclusions: Resistance-type exercise performed in the evening augments the overnight muscle protein synthetic response to presleep protein ingestion and allows more of the ingested protein-derived amino acids to be used for de novo myofibrillar protein synthesis during overnight sleep.
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http://dx.doi.org/10.1249/MSS.0000000000001045DOI Listing
December 2016

Physical Activity Performed in the Evening Increases the Overnight Muscle Protein Synthetic Response to Presleep Protein Ingestion in Older Men.

J Nutr 2016 07 8;146(7):1307-14. Epub 2016 Jun 8.

NUTRIM School of Nutrition and Translational Research in Metabolism and Top Institute Food and Nutrition (TIFN), Wageningen, Netherlands; and

Background: The age-related decline in skeletal muscle mass is partly attributed to anabolic resistance to food intake. Dietary protein ingestion before sleep could be used as a nutritional strategy to compensate for anabolic resistance.

Objective: The present study assessed whether physical activity performed in the evening can augment the overnight muscle protein synthetic response to presleep protein ingestion in older men.

Methods: In a parallel group design, 23 healthy older men (mean ± SEM age: 71 ± 1 y) were randomly assigned to ingest 40 g protein intrinsically labeled with l-[1-(13)C]-phenylalanine and l-[1-(13)C]-leucine before going to sleep with (PRO+EX) or without (PRO) performing physical activity earlier in the evening. Overnight protein digestion and absorption kinetics and myofibrillar protein synthesis rates were assessed by combining primed, continuous infusions of l-[ring-(2)H5]-phenylalanine, l-[1-(13)C]-leucine, and l-[ring-(2)H2]-tyrosine with the ingestion of intrinsically labeled casein protein. Muscle and blood samples were collected throughout overnight sleep.

Results: Protein ingested before sleep was normally digested and absorbed, with 54% ± 2% of the protein-derived amino acids appearing in the circulation throughout overnight sleep. Overnight myofibrillar protein synthesis rates were 31% (0.058% ± 0.002%/h compared with 0.044% ± 0.003%/h; P < 0.01; based on l-[ring-(2)H5]-phenylalanine) and 27% (0.074% ± 0.004%/h compared with 0.058% ± 0.003%/h; P < 0.01; based on l-[1-(13)C]-leucine) higher in the PRO+EX than in the PRO treatment. More dietary protein-derived amino acids were incorporated into de novo myofibrillar protein during overnight sleep in PRO+EX than in PRO treatment (0.042 ± 0.002 compared with 0.033 ± 0.002 mole percent excess; P < 0.05).

Conclusions: Physical activity performed in the evening augments the overnight muscle protein synthetic response to presleep protein ingestion and allows more of the ingested protein-derived amino acids to be used for de novo muscle protein synthesis during overnight sleep in older men. This trial was registered at Nederlands Trial Register as NTR3885.
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http://dx.doi.org/10.3945/jn.116.230086DOI Listing
July 2016

Body Position Modulates Gastric Emptying and Affects the Post-Prandial Rise in Plasma Amino Acid Concentrations Following Protein Ingestion in Humans.

Nutrients 2016 Apr 13;8(4):221. Epub 2016 Apr 13.

Department of Human Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, P.O. Box 616, Maastricht 6200 MD, The Netherlands.

Dietary protein digestion and amino acid absorption kinetics determine the post-prandial muscle protein synthetic response. Body position may affect gastrointestinal function and modulate the post-prandial rise in plasma amino acid availability. We aimed to assess the impact of body position on gastric emptying rate and the post-prandial rise in plasma amino acid concentrations following ingestion of a single, meal-like amount of protein. In a randomized, cross-over design, eight healthy males (25 ± 2 years, 23.9 ± 0.8 kg·m(-2)) ingested 22 g protein and 1.5 g paracetamol (acetaminophen) in an upright seated position (control) and in a -20° head-down tilted position (inversion). Blood samples were collected during a 240-min post-prandial period and analyzed for paracetamol and plasma amino acid concentrations to assess gastric emptying rate and post-prandial amino acid availability, respectively. Peak plasma leucine concentrations were lower in the inversion compared with the control treatment (177 ± 15 vs. 236 ± 15 mmol·L(-1), p < 0.05), which was accompanied by a lower plasma essential amino acid (EAA) response over 240 min (31,956 ± 6441 vs. 50,351 ± 4015 AU; p < 0.05). Peak plasma paracetamol concentrations were lower in the inversion vs. control treatment (5.8 ± 1.1 vs. 10.0 ± 0.6 mg·L(-1), p < 0.05). Gastric emptying rate and post-prandial plasma amino acid availability are significantly decreased after protein ingestion in a head-down tilted position. Therefore, upright body positioning should be considered when aiming to augment post-prandial muscle protein accretion in both health and disease.
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http://dx.doi.org/10.3390/nu8040221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4848689PMC
April 2016

What is the Optimal Amount of Protein to Support Post-Exercise Skeletal Muscle Reconditioning in the Older Adult?

Sports Med 2016 Sep;46(9):1205-12

Department of Human Movement Sciences, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+ (MUMC+), PO Box 616, 6200 MD, Maastricht, The Netherlands.

Hyperaminoacidemia following protein ingestion enhances the anabolic effect of resistance-type exercise by increasing the stimulation of muscle protein synthesis and attenuating the exercise-mediated increase in muscle protein breakdown rates. Although factors such as the source of protein ingested and the timing of intake relative to exercise can impact post-exercise muscle protein synthesis rates, the amount of protein ingested after exercise appears to be the key nutritional factor dictating the magnitude of the muscle protein synthetic response during post-exercise recovery. In younger adults, muscle protein synthesis rates after resistance-type exercise respond in a dose-dependent manner to ingested protein and are maximally stimulated following ingestion of ~20 g of protein. In contrast to younger adults, older adults are less sensitive to smaller doses of ingested protein (less than ~20 g) after exercise, as evidenced by an attenuated increase in muscle protein synthesis rates during post-exercise recovery. However, older muscle appears to retain the capacity to display a robust stimulation of muscle protein synthesis in response to the ingestion of greater doses of protein (~40 g), and such an amount may be required for older adults to achieve a robust stimulation of muscle protein synthesis during post-exercise recovery. The aim of this article is to discuss the current state of evidence regarding the dose-dependent relationship between dietary protein ingestion and changes in skeletal muscle protein synthesis during recovery from resistance-type exercise in older adults. We provide recommendations on the amount of protein that may be required to maximize skeletal muscle reconditioning in response to resistance-type exercise in older adults.
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http://dx.doi.org/10.1007/s40279-016-0504-2DOI Listing
September 2016

Hsp25 and Hsp72 content in rat skeletal muscle following controlled shortening and lengthening contractions.

Appl Physiol Nutr Metab 2014 Dec 26;39(12):1380-7. Epub 2014 Aug 26.

Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON M5S 2W6, Canada.

The cytoprotective proteins, Hsp25 and Hsp72, are increased in skeletal muscle after nondamaging, shortening contractions, but the temporal pattern of expression and stimulatory mechanisms remain unclear. Thus, we sought to define the in vivo temporal patterns of expression for Hsp25 and Hsp72 after 2 opposing contractions types. To do this, male Sprague-Dawley rats had 1 tibialis anterior (TA) muscle electrically stimulated (5 sets of 20 repetitions) while being either forcibly lengthened (LC) or shortened (SC). At 2, 8, 24, 48, 72, or 168 h after the contractions both the stimulated and the nonstimulated (contra-lateral control) TA muscles were removed and processed to examine muscle damage (hemotoxylin and eosin staining) and Hsp content (Western blot analyses). Cross-sections from TA muscles subjected to LCs showed muscle fibre damage at 8 h and thereafter. In contrast, no muscle fibre damage was observed at any time point following SCs. When normalized to contra-lateral controls, Hsp25 and Hsp72 content were significantly (P < 0.01) increased at 24 h (3.1- and 3.8-fold, respectively) and thereafter. There were no significant increases in Hsp25 or Hsp72 content at any time point following SC. These data suggest that LCs, but not SCs, result in Hsp accumulation and that the fibre/cellular damage sustained from LCs may be the stimulus for elevating Hsp content.
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http://dx.doi.org/10.1139/apnm-2014-0118DOI Listing
December 2014

Refining dietary protein recommendations for the athlete.

J Physiol 2013 Jun;591(12):2967-8

Department ofHumanMovement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre+, Maastricht, 6200 MD, The

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http://dx.doi.org/10.1113/jphysiol.2013.255927DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3832112PMC
June 2013
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